In the related art, electronic devices include an internal circuit that performs signal processing and a DC-DC converter that supplies an output voltage as a power voltage to the internal circuit. The DC-DC converter generates an output voltage to be supplied to the internal circuit from an input voltage and performs control so that the output voltage is constant. In order to perform the control so that the output voltage is constant, the DC-DC converter performs feedback control.
However, in the DC-DC converter, there is a problem in terms of stability in a control system (feedback loop) that controls the feedback control due to frequency characteristics of elements that form the feedback loop, For example, in the DC-DC converter, the output voltage undesirably oscillates due to a drastic change in the output voltage. Therefore, an error amplifier that constitutes the DC-DC converter is normally equipped with a phase compensation unit between an output terminal and a negative input terminal thereof so as to maintain the stability of the output voltage.
Regarding a constant (phase compensation constant) of this phase compensation unit, an optimal phase compensation constant varies depending on the conditions of the input voltage and the output voltage of the DC-DC converter (input/output conditions). Therefore, the DC-DC converter selects one phase compensation constant within a limited range of input/output conditions so as to stably generate an output voltage. Consequently, the DC-DC converter is problematic in that it cannot select an optimal phase compensation constant within the entire range of input/output conditions.
As a countermeasure against this problem, the DC-DC converter of the related art is provided with a plurality of different phase compensation constants and switches the phase compensation constants in accordance with the input-output conditions (see Japanese Patent Application Laid-open No. 2005-110468). Thus, the DC-DC converter can select an optimal phase compensation constant with respect to the input/output conditions corresponding to the phase compensation constants provided therein.